Introduction: Migraine is a prevalent and disabling neurological disorder with a complex, partially understood pathophysiology. Red blood cell distribution width (RDW), a routine hematological parameter, has emerged as a potential biomarker of systemic inflammation, which may be relevant in migraine.
Methods: We conducted a systematic review and meta-analysis of studies reporting RDW values in individuals with and without migraine. Electronic databases (PubMed, Scopus, Web of Science) and Google Scholar were searched through June 23, 2025. Inclusion criteria comprised case-control studies comparing RDW in migraineurs and healthy controls.
Results: Five case-control studies comprising 1,240 participants (709 with migraine, 531 without) met the inclusion criteria. RDW values were higher in migraine patients in four of the five studies. The overall pooled weighted mean difference (WMD) in RDW was 0.24 (95% CI: –0.15 to 0.62; I² = 97%). After excluding one outlier study the WMD increased to 0.47 (95% CI: 0.18 to 0.76).
Discussion and Conclusion: Our findings suggest a trend toward elevated RDW in individuals with migraine. While promising, the results are limited by high heterogeneity and methodological inconsistencies across studies, underscoring the need for further standardized research.

Keywords: RDW, Red blood cell distribution width, Migraine